Selective hydrogenation of nitriles to secondary amines catalyzed by a pyridyl-functionalized and alkenyl-tethered NHC-Ru(II) complex

A set of Co(III) and Ru(II) compounds are synthesized bearing pyridyl-functionalized and alkenyltethered N-heterocyclic carbene (NHC) ligand (L-1). [Co-III(L-1)(3)](PF6)(3) (1) was synthesized by the reaction of [(LH)-H-1]PF6, Co(OAc)(2)center dot 4H(2)O, K2CO3 in tetrahydrofuran (THF) under refiuxing condition. [(RuL1)-L-II(eta(6)-p-cymene)CI]PF6 (2) was synthesized via transmetallation method. For both compounds, the NHC ligand chelates the metal through carbene carbon and pyridyl nitrogen whereas the butenyl unit remains free. Compound 2 hydrogenates organic nitriles efficiently providing selectively secondary amines. In the presence of external amines, unsymmetrical secondary amines are also obtained. (C) 2015 Elsevier B.V. All rights reserved.